Coupling of diffusion-induced and thermal stresses in solid-state lithium-ion batteries: A fully 3D electrochemical-thermal-mechanical model

Solid-state lithium batteries (SSLBs) are prone to mechanical degradation due to the coupling effect of diffusion-induced stress and thermal stress during operation. To systematically reveal the spatial distribution characteristics of internal stress and its evolution mechanism within the battery, a fully three-dimensional electrochemical-thermal-mechanical coupling model was developed based on the actual stacking-layer geometry. The model overcomes the homogeneity assumption in the electrode thickness direction inherent in traditional one-dimensional electrochemical models and accurately captures non-uniform effects, such as current distribution and local stress concentration, through three-dimensional electrochemical modeling. The model was verified by comparing it with the experimental data from constant current charging tests, and it simulated the evolution law of internal stress under different charging rates ranging from 0.5C to 2C. The results show that as the charging rate increases, the diffusion stress decreases, while the thermal stress significantly increases; although the total stress shows a decreasing trend at the end of charging, the proportion of thermal stress increases significantly from 3% at 0.5C to 21% at 2C. This study provides theoretical support for multi-physics field coupling modeling and thermal management strategies under high-rate fast charging conditions.